What Is an Expansion Tank in a Boiler?

For your boiler to operate correctly, it needs to maintain steady pressure in its hot water tank and throughout its pipes. Water pressure will increase as the water in the system heats up, so the boiler comes with a number of methods to keep the pressure from reaching levels where it can cause damage. One of the ways a boiler maintains a safe pressure level is with an expansion tank. We will explain how this crucial component of a boiler operates—and why it’s important to keep it maintained and repaired.

For immediate repairs on your boiler in Oak Grove, MN, whether because of trouble in the expansion tank or any other malfunction, you can call Air Mechanical, Inc. 24 hours a day, 7 days a week.

What an expansion tank does

The name “expansion tank” makes it sound as if it stores extra water for additional heating. Boilers don’t actually work that way. The expansion tank is there to provide an air cushion against extra pressure from inside the main tank.

The expansion tank sits atop the hot water tank: if you go look at your boiler right now, you’ll see a smaller tank hooked to a pipe coming from the top of the main tank that enters the smaller tank from the side. The interior consists of two sections with a rubber diaphragm separating them. The pipe that comes from the tank will fill one side with water. The other side contains pressured air connected to a valve to measure the pressure. The valve will add air to keep a balance with the water on the other side. An increase in water pressure pushes against the membrane and relieves the pressure from the main tank. When the water pressure drops, the air pressure from the other side pushes back to restore it to normal.

The invention of the expansion tank was designed to combat corrosion in the main tank: older boilers relied on a cushion of air within the tank itself, but this permitted too much oxygen into the water, which is a main part of the oxidation that results in corrosion.

Make sure to repair/replace the expansion tank in your boiler

Ruptures or leaks in the diaphragm in the expansion tank can lead to the boiler overheating from increased pressure. The expansion tank usually should be replaced, but this requires the work of a professional to make sure it is done correctly and the pressure problems stop.

If you need repairs or replacement for the expansion tank on your boiler in Oak Grove, MN, get in touch with Air Mechanical, Inc. right away—any time of the day or night. We have a quarter of a century of experience working with boilers and many other types of heating and cooling systems. We can fix your boiler fast and get it done right the first time. Or feel free to check out other heating services we offer in Oak Grove.